Here's what Japan says happened to the F-35 that mysteriously disappeared in the Pacific

japan f 35

JASDF's 3rd Air Wing, 302nd Tactical Fighter Squadron, Misawa Air Base, Japan.

The aircraft, designated AX-6, is the second F-35A assembled at Mitsubishi Heavy Industries' F-35 Final Assembly & Check-Out (FACO) facility in Nagoya, Japan and is the first to be assigned to the JASDF's 3rd Air Wing, 302nd Tactical Fighter Squadron, Misawa Air Base, Japan.

  • The Japanese defense ministry said Monday that it believes the F-35A Lightning II Joint Strike Fighter lost in April occurred after the 41-year-old pilot Maj. Akinori Hosomi succumbed to "vertigo or spatial disorientation."
  • The aircraft, following a rapid descent from a much higher altitude, disappeared from radar on April 9 while flying at speeds of almost 700 mph only 1,000 feet above the Pacific Ocean.
  • The pilot, who was pronounced dead last week, did not sent out a distress signal, try to eject, or respond to warnings from the fighter's proximity sensors, which were presumably alerting him of an imminent collision.
  • While the ministry has ruled out a loss of consciousness or any technical problems with the fifth-gen fighter, all of Japan's F-35s remain grounded while pilots re-train on critical skills.
  • Japan has officially called off its search for the missing fighter jet, which the defense ministry reports was destroyed in the crash.
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The F-35 that went missing in April crashed after the pilot lost his spatial awareness and slammed the fighter into the Pacific Ocean at almost 700 mph, the Japanese defense ministry said Monday, according to multiple reports.

A Japan Air Self-Defense Force (JASDF) F-35A Joint Strike Fighter piloted by Maj. Akinori Hosomi of the 3rd Air Wing's 302nd Tactical Fighter Squadron mysteriously vanished from radar on April 9 about 85 miles east of Misawa Air Base.Advertisement

The US and Japan dispatched military assets to assist in search and rescue operations. The US ended its search in May, but the Japanese military kept going until last week.

Read more: An F-35 stealth fighter is still missing somewhere in the Pacific - here's everything the US military has sent to find it

"We believe it highly likely," Defense Minister Takeshi Iwaya explained to reporters Monday, "the pilot was suffering from vertigo or spatial disorientation and wasn't aware of his condition. It can affect any pilot regardless of their experience." The 41-year-old major had over 3,200 flight hours, including 60 hours on the F-35, under his belt at the time of the crash.

Japan F-35

US Air Force/Tech. Sgt. Benjamin W. Stratton

Senior leaders from Japan's Ministry of Defense, US Forces Japan, Pacific Air Forces, and Lockheed Martin at a Japan Air Self-Defense Force hangar to welcome the first operational F-35A Lightning II to JASDF's 3rd Air Wing, at Misawa Air Base, Japan, February 24, 2018.

This conclusion was reached after careful analysis of the radar and flight control data, as well as conversations with other F-35 pilots.The pilot did not send out a distress signal indicating that he thought he was in trouble, and there is no indication he tried to eject. Furthermore, there is no evidence the major tried to pull up as the fighter's onboard proximity warning system, which was presumably alerting him of an imminent collision, Reuters reported.Advertisement

The Japanese defense ministry has ruled out a loss of consciousness or any problem with the plane as an explanation for the crash. Nonetheless, all Japanese F-35 pilots are being re-trained on avoiding spatial disorientation and gravity-induced loss of consciousness. All of its stealth fighters are currently grounded.

The ministry said in a statement that the fifth-generation fighter, following a rapid descent from an altitude of 31,500 feet, was flying 1,000 feet above the ocean's surface at a speed of about 1,100 kph (683 mph) when the jet inexplicably disappeared from radar, according to Stars and Stripes. The defense ministry explained that the aircraft was destroyed "and parts and fragments scattered across the sea bottom."

On June 3, Japan called off the search for the missing fighter and the remains of the pilot, who was declared deceased at a press conference on June 7 after it was confirmed that body parts found among wreckage discovered shortly after the accident were those of Maj. Hosomi.Advertisement

Read more: Wreckage from crashed Japanese F-35 fighter found, pilot still missing

The flight data recorder was found during a later deep-water search, but the memory was lost, leaving many questions unanswered.

Read more: More pieces of Japan's missing F-35 have been found, but what happened to the stealth fighter remains a mysteryAdvertisement

"It is truly regrettable that we lost such an excellent pilot," Iwaya said late last week. "We truly respect Maj. Hosomi, who was lost while devotedly performing his duty and we extend our heartfelt condolences and offer our deepest sympathies to the family."